Keeping Cats away is fairly easy. There are 4 ways of doing it :-
1. Cats do not like citrus smells, so leaving Orange or Lemon peel around keeps them away, and it does smell OK.
2. Cats respect larger Cats, so visit a local Zoo and get some Lion or Tiger poo and spread this around. The cats will think a larger animal lives there and will keep away. However, the smell might keep you away aswell.
3. Spray Pepper around, as it irritates their noses and makes them sneeze. Cats can get a fatal disease called 'Cat Flu' so sneezing to a cat makes them think they are very ill and will keep away.
4. Cats and Dogs can hear sounds that humans cannot, so if you play a CD of those noises, the cats will not stay. The final track on the Beatles 'Sergeant Peppers' LP includes those sounds as John Lennon didn't like Cats or Dogs.
Hopes this helps.